1. Field of the Invention
The present invention relates to a network system which is capable of transmission and reception of voice information using communication means.
2. Description of the Prior Art
In recent years, voice mail has been used at a practical level. In this voice mail, a message is input in voice using a computer systems, and the input voice information is sent to a local or remote computer through a network. At the local or remote computer, reproduction of the message is performed.
Voice mail is an excellent information transmission media because it has the excellent recordability possessed by document-oriented electric mail, that is, because it is capable of transmission of a message even when an addressee is absent, and because it has the high speed of the information transmitted in voice.
Transmission and reception of voice mail are performed in the manner described below: an audio message is input from a terminal unit provided with a voice input unit generally consisting of a microphone, an A/D converter, and a data compression unit, when necessary. The message is transmitted to the terminal unit which is an addressee in accordance with the transmission procedure of the network in the form of a file. At the terminal unit, which is the addressee, reverse conversion of the transmitted voice mail file is conducted in accordance with the communication protocol between the addressee and the addressor. Thereafter, a D/A converted message passes through an amplifier and then drives a speaker which makes the message audible to a receiver.
Transmission and reception of voice mail require special hardware. For transmission of voice mail, at least a microphone and an A/D converter are necessary. At the reception side, a D/A converter, an amplifier, a speaker and so on are necessary. The fact that the special hardware is required for transmission and reception of voice mail gives rise to a problem in that a transmitted message cannot be conveyed when the reception side of the voice mail does not have a voice reproducing hardware, and in that the cost of the hardware is quite high.